Recent work in the field of olefin upgrading has resulted in a catalytic process for converting lower olefins to heavier hydrocarbons. Heavy distillate and lubricant range hydrocarbons can be synthesized over ZSM-5 type catalysts at elevated temperature and pressure to provide a product having substantially linear molecular conformations due to the ellipsoidal shape selectivity of certain medium pore catalysts.
Conversion of olefins to gasoline and/or distillate products is disclosed in U.S. Pat. Nos. 3,960,978 and 4,021,502 (Givens, Plank and Rosinski) wherein gaseous olefins in the range of ethylene to pentene, either alone or in admixture with paraffins are converted into an olefinic gasoline blending stock by contacting the olefins with a catalyst bed made up of a ZSM-5 type zeolite. Particular interest is shown in a technique developed by Garwood, et al., as disclosed in European patent application No. 83301391.5, published Sept. 29, 1983. In U.S. Pat. Nos. 4,150,062; 4,211,640 and 4,227,992 Garwood et al disclose the operating conditions for the Mobil Olefin to Gasoline/Distillate (MOGD) process for selective conversion of C.sub.3 + olefins to mainly aliphatic hydrocarbons.
In the process for catalytic conversion of olefins to heavier hydrocarbons by catalytic oligomerization using a medium pore shape selective acid crystalline zeolite, such as ZSM-5 type catalyst, process conditions can be varied to favor the formation of hydrocarbons of varying molecular weight. At moderate temperature and relatively high pressure, the conversion conditions favor C.sub.10 + aliphatic may be converted; however, the distillate mode conditions do not convert a major fraction of ethylene. A typical reactive feedstock consists essentially of C.sub.3 -C.sub.6 mono-olefins, with varying amounts of nonreactive paraffins and the like being acceptable components.
U.S. Pat Nos. 4,520,221, 4,568,786 and 4,658,079 to C. S. H. Chen et al., incorporated herein by reference in their entirety, disclose further advances in zeolite catalyzed olefin oligomerization. These patents disclose processes for the preparation of high viscosity index lubricant range hydrocarbons by oligomerization of light olefins using zeolite catalyst such as ZSM-5. The oligomers so produced are essentially linear in structure and contain olefin unsaturation. These unique olefinic oligomers are produced by surface deactivation of the ZSM-5 type catalyst by pretreatment with a surface-neutralizing base.
The formulation of lubricants typically includes an additive package incorporating a variety of chemicals to improve or protect lubricant properties in application specific situations, particularly internal combustion engine and machinery applications. The more commonly used additives include oxidation inhibitors, rust inhibitors, antiwear agents, pour point depressants, detergent-dispersants, viscosity index (VI) improvers, foam inhibitors and the like. This aspect of the lubricant arts is specifically described in Kirk-Othmer "Encyclopedia of Chemical Technology", 3rd edition, Vol 14, pp 477-526, incorporated herein by reference. The inclusion of additives in lubricants provides a continuing challenge to workers in the field to develop improved additives of increased compatibility with the lubricant and other additives or new additives containing a multifunctional capability that can reduce the number of additives required in the formulation.
The aforementioned olefinic character of the lower olefin oligomers produced by the ZSM-5 catalyzed processes of Chen et al. provides a reactive site to modify those unique oligomers to produce derivatives that can exhibit lube additive properties or improvements in lubricant characteristics. Olefin epoxidation is one known reaction which can be readily applied to a variety of olefinic compounds. Further, it is known that epoxides can be converted to 1,2-glycols. Such glycols can be prepared by hydrolysis of a separated epoxide or prepared directly from the olefin without prior separation of the epoxide. Conventionally, this is carried out by in situ formation of a peracid to oxidize the olefin to the epoxide followed by hydrolysis of the epoxide to the 1,2-glycol. The preparation of epoxides is described in Chapter 7 of Synthetic Organic Chemistry, R. Wagner and H. Zook, published by John Wiley & Sons, Inc. and hydrolysis of epoxides to 1,2-glycols is described in Chapter 5, page 172. Epoxidation and hydroxylation of alkenes is further described in Advance Organic Chemistry, by E. Royals, published by Prentice-Hall, pages 331-335. Both the Wagner and Zook and Royals references are incorporated herein by reference.
It is also known that 1,2-glycols, such as those formed from cleavage of epoxides, can be esterified by methods well known in the art to form a wide variety of esters.
Accordingly, is an object of the present invention to provide a process for the hydroxylation of olefins produced by zeolite catalyzed oligomerization of lower olefins.
Another object of the present invention to provide a process for the esterification of the hydroxylated olefins produced by hydroxylation of zeolite catalyzed oligomerization of lower olefins.
It is another object of the present invention to provide novel lubricant additives and lubricants by the hydroxylation and esterification of olefin oligomers produced from lower olefins by surface deactivated zeolite catalysts.
Yet another object of the instant invention is to provide novel lubricant mixtures from mineral oil and synthetic lubricants derived from polyalphaolefins (PAO) and containing hydroxylated and/or esterified olefin oligomers.